National DEM workshop strategises way ahead

September 1st, 2014, Published in Articles: PositionIT, Featured: PositionIT


The Department of Rural Development and Land Reform (DRDLR) and the South African National Space Agency held a National DEM User Need and Strategy Workshop on 20 August 2014 in Pretoria. The workshop was attended by representatives from the geospatial industry including: the Agricultural Research Council; Airbus; ATNS; CSIR; the Departments of Agriculture, Forestry and Fisheries, Defence, Environmental Affairs, and Water and Sanitation; Eskom; the Council for Geoscience; GeoTerraImage; the Housing Development Agency; Manco-Aurecon; Optron; SAGI; SANRAL; SMC Synergy; SITA; Southern Mapping; StatsSA; Transnet; the University of Stellenbosch; and Vodacom.

SANSA’s Dr. Jane Olwoch welcomed the participants to the workshop and Dr. Derek Clarke from the DRDLR’s National Geo-spatial Information (NGI) explained that the purpose of the workshop was to review the current status of Digital Elevation Models (DEM) in South Africa and to determine the user requirements in terms of accuracy, resolution, update frequency and formats for a national DEM.


Aslam Parker, Dr. Jane Olwoch, Dr. Derek Clarke, Aubrey Kekana, and Dr. Paida Mangara.

NGI’s Aslam Parker spoke about DEMs and their application in South Africa and explained the difference between DEM, Digital Terrain Models (DTM), and Digital Surface Models (DSM). He was followed by Raoul Duesimi (NGI) who spoke about NGI’s National Elevation Programme, the available elevation products, and NGI’s DEM requirements.

Following this the workshop focused on the user requirements for a national DEM with representatives from SANSA; the Departments of Agriculture, Forestry and Fisheries, Environmental Affairs, and Water and Sanitation;  Eskom; GeoTerraImage; the CSIR; and SPLUM (DRDLR) giving presentations on how their organisations make use of DEMs, the current limitations experienced, and their required specifications for a national DEM.

Julie Verhulp (NGI) shared the results of a user needs survey that was carried out prior to the workshop. Respondents indicated the following:

  • The resolution of the NGI 25 m DEM is too low and that it has limited coverage.
  • The Stellenbosch University DEM (SUDEM) is good with high resolution, but is too expensive and is not well known.
  • The RSA 20 m DEM is not well known.
  • The ASTER GDEM has poor accuracies.
  • The SRTM DEM (30 and 90 m) is good but its resolution is too coarse.

The 37 survey respondents were generally positive about NGI  taking on this initiative with 87% believing that the national DEM should be free as the benefits of having high-quality, freely available elevation data are far more valuable than the revenue it might generate.

Presentations were then given by DEM producers including Willard Mapurisa (SANSA), Adrian van Niekerk (University of the Stellenbosch),  Dr. Corne Eloff (Airbus), and Norman Banks (Southern Mapping).  During his presentation, Mapurisa said there was a need for high resolution DEMs to support land use planning, radio network planning, hydrological modelling and disaster mitigation but that it was evident that the high resolution DEM options currently available are expensive and that perhaps South Africa needs to adopt a multi-sensor, multi-source approach.

Next, Van Niekerk spoke on SUDEM, detailing its background and how it compares to other DEMs. He said that a new SUDEM release would be available in October 2014. He was followed by Eloff, who spoke on his company’s product World DEM saying that it is homogenous, seamless and consistent, and that further African data will be available in 2015. Last up was Norman Banks from Southern Mapping who outlined the various airborne acquisition methods carried out by his aerial survey company, pointing out that users have variable multi-accuracy and re-visit requirements.

A working group was established at the close of the meeting which will work towards tackling key issues such as creating a South African DEM inventory; specifications relating to frequency, resolution and accuracy; the outputs for different users; the funding model and so on. NGI will take the lead in this national DEM initiative as it is the custodian of national elevation data, however, it was pointed out by Dr. Derek Clarke that developing a national DEM is a collaborative effort and that the geospatial sector will need to pool its efforts to ensure that the objectives of the workshop are met.

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